“Precision” or “does NOT do what it says on the tin”

[mgjParticipant @mgj]

You take the chuck off and put a test bar in the mandrel, and clock on that.

 

Beware though. Some clocks are more equal than others.

 

Or, you do the standard turning test and adjust said lathe till it is parallel.

[Chris TriceParticipant @christrice43267]

Posted by peter walton on 28/03/2010 12:23:10:

Just a question to the OP, how do you know that at 5 – 6 inches your lathe is running parallel the lathe bed.

I would like to know as I am not sure how one is supposed to check this if there is no prior knowledge to the present chucks accuracy!

 

peter

 

In the context of this thread, the problem is that the collet refuses to hold the piece inline with the headstocks axis of rotation because the tailend of the collet is (was) too small and unsupported, hence it wobbles. If the collet and chuck were accurate, the test piece wouldn’t wobble. The headstock axis not being parallel with the lathe bed is a different issue which would cause any workpiece to be turned tapered but it would be a true running taper. I’m making a huge assumption that you might be not understanding the problem so apologies in advance if you’re just posing a question about checking parallelism generally.

[VersabossParticipant @versaboss]

Hmm, did I get something wrong here too? Afaik a C type collet has a very similar form to the more usual W types in use here in my country. I was thinking that these collets are centralized by the front cone and not by the tail end ( which anyway finally is guided by the draw tube). I never checked the tail diameters of my collets (and the inside spindle dia. of the lathe), maybe I will have to do that…

Greetings, Hansrudolf

[Dinosaur EngineerParticipant @dinosaurengineer]

I think the main problem in buying things like collets and other precision workshop items is we old timers automatically think they will be the same quality as the equivalent British items were and they will be ” fit for purpose” . Those days are now clearly over for items supplied by far eastern manufacturers and we now have to ask for specifications or accuracy to stand any chance that what we order is what we think it is.How many DROs do see advertised that specify the readout resolution but not the accuracy ? Machine test bars that do not say they are left soft ,etc. it also doesn’t help when the importers do not have the knowledge or experience to understand the limitations of what they are supplying. I often wonder is this situation the same in countries such as Germany with a similar background in engineering industries.?  Or is it a case of Rip Of Britain ?

[BogstandardParticipant @bogstandard]

To get back to the original post, rather than bitching about far eastern products,

 

I have now fitted, over the last few years and machine changes, four of these 5C collet chucks.

 

I too thought that my collets were out, but far from it, I have well over a hundred of the things, bought from all sources and suppliers, cheapo far eastern stuff, and I think the most runout I have come across is about 2/10ths. Well within my requirements.

 

I soon found the problem was the tapered nose in the chucks themselves. 

 

I always take great care with my back mounting, no silly things like warming up the chuck and having a shrink fit, that causes more problems than it solves, just good general engineering to get a very fine fit. Once that is done, get out the toolpost grinder and true up the internal taper, you would be very surprised how far these can be out. Most times you can actually see it wobbling if you run it up without a collet in. Five or six thou is about average, but one of them required 15 thou grinding out before it ran perfectly true. For that one, because so much was taken out, I had to remove 1/8″ from the front of the chuck to get the collet protruding correctly, as it had sunk inside when tightened up.

 

I have no qualms about naming names, that real bad one was a D1-4 mount 5C chuck from Chronos, and when checking out the internals, it looked like it was made by a caveman with a flint axe. But my ‘fix’ turned it into a very accurate chuck, just like the other three I have done. No thoughts about returning it, as you can just as easily get one that is even worse. Just get on and ‘fix’ it, or get your money back and forget about it.

 

I know everyone will jump on the bandwagon about far eastern crap, but by gentle persuasion and fixing the little faults, with my tweaked crap, I can turn out stuff far more accurately than the ‘elite’ machines and tooling owned by a lot of people. You work with what you can afford, and if that means putting a few things right, then that is the way you need to go.

 

Also remember, a machine is only as good as the operator and how well he/she has set it up.

Unless you are in a position where you can say your machine and it’s related tooling is set up correctly, can you comment about such things.

 

Bogs

[NJHParticipant @njh]

Hear hear Bogs. One can’t expect a Rolls Royce for the price of a Mini but, with the appropriate care and treatment,  both we get you to your destination!

[Richard ParsonsParticipant @richardparsons61721]

 

Someone wrote somewhere in site that ‘Cheap Chinese lathes’ should be regarded as a kit of parts and will need building up.  The same is true of collets sets, chucks etc. My big Chinese lathe took nearly 6 months of patient cleaning, scraping etc. to get it right. I had my hooks on a Dean Smith and Grace which used in my name sake’s tool rooms before they built the main engines for old Noah’s Ark. I could not bring it out of the UK because it was not on the DTI’s data base of machines and I was damned if I was going to provide a full set for drawings for it.

As Mr. Bogstandard says you have to fit the collet-holders to your machine and get them true.  For this reason I only buy collets and make my own holders. I bought a set of second hand Russian collets 4mm to 14mm by 0.5 mm steps for about £25.  I then made a holder and they are 0.005 mm max run out. I also do a standard alignment check on my lathes once every 3 months and again before I am going to have to do something which requires great accuracy. I only takes 5 or so minutes to do.

As to spending more money, well some western companies can turn out pretty good junk at times.  No one does 100% inspection and as the chief Chinese inspector Mr Wun Thou Wong says ‘You no gettee light allee time”.

[DiggerParticipant @digger]

Hello all, This is my first post here and this thread in particular makes for some good reading. Until quite recently I worked in the aerospace industry using some fantastic machine tools that would cost upwards of a million quid, of course accuracy in the aero industry is paramount, but the company had the wads of cash to throw into the tooling and machinery, I now have a small workshop at home i have a conquest lathe from chester and a little cmd10 mini mill from clarke, I did laugh when i first ran a clock over the machine bed on the mill, but I wasn’t at all surprised, I don’t think that is is realistic for any of us to expect serious accuracy from any of theses cheaper imported machines or their tooling and I agree with Bogs, the slight inaccuracies of the imported tooling that we can buy for little money is a small inconveinience and is usually a quite straightforward matter for an engineer to put right, it may sometimes be a little annoying when things aren’t running true, but it’s a bit of fun to put them right before getting on with the business of producing a part.

[john swift 1Participant @johnswift1]

100% inspection does not guarantee any thing !

about  25 years ago , an aunt worked for a local company making gas stoves and cookers

and one day she told us , rejected parts had been used to keep the production line working !

 

final quality control is left to the end user

 

[DiggerParticipant @digger]

Yes I agree with that especially for commercial household products inspection is probably more of an afterthought, for work that is supposed to be very precise the parts should be self checked by the machinist and then again by an unbiased inspector who is totally impartial, but that is meaningless if the parts are being produced en mass by unqualified people which is probably the case with oriental products.

[BogstandardParticipant @bogstandard]

“but that is meaningless if the parts are being produced en mass by
unqualified people which is probably the case with oriental products.”

 

To me, that is a very unjustified comment.

 

Almost anywhere in the world nowadays, mass production is carried out using CNC machining centres, very rarely controlled by skilled setters any more, but semi skilled workers.

All the main work is done off floor by programmers.

 

Where the difference occurs is in the assembly of the items. Remember the word ‘assembly’, because that is where the main difference lies.

 

In the far east, hobby machines are usually ‘assembled’ not ‘fitted’ together. That is the major factor. The bits are put into position, just to make sure they fit together and left at that

 

If you are willing to carry out that fitting yourself, then go for something made in the far east and save yourself loadsa money.

If you are incapable of doing that, then you are at the mercy of companies who will supply you with a ready fitted machine (Myford for example) and you will be paying for that ‘fitting’ together. Way over the top in most cases. Plus, unless you can keep up with adjusting the machine, which needs to be done regularly, you will just end up with another load of castings that are no better than the assembled machines from the far east.

In fact you will be worse off, because again using Myford as an example, designed well over 60 years ago and too small for the larger engineering projects that we get up to. When you can buy a far eastern machine for a third of the price that comes with everything already on board, plus double the swing.

I know which one I will go with.

 

You have to accept that resting on your reputational laurels only goes so far in this day and age, value for money makes more of an impact.

Just give it a few more years, when the far east starts to sell ‘fitted’ hobby machines, then the  ‘elitist’ band of engineers will certainly know their days are numbered.

 

You could see how it was going fifteen to twenty years ago. Very poor quality machine tools and tooling were coming in, but now things are 1000% better, and getting better all the time. Forty years ago, who in their right mind would have bought Japanese precision instruments, now everyone clamours after them, saying they are the best thing since sliced bread.

 

The far east are already doing fantastic fitting and setting on semi industrial and industrial machines. A lot more than you think, hobby machines and tooling are just a cheapo sideline to them.

 

I bought a semi industrial mill for one third the cost of one produced over here, and that was delivered and has been running for nearly two years with no fitting or adjustments required at all,  except for one bearing, which was a ten minute job and didn’t have to be done, just me being picky.

 

It had been set up and fitted perfectly.

 

Don’t be like the three monkeys. No matter what you do, they are here, and here to stay, and will only improve as time goes on.

 

Don’t get me wrong, I have had ‘badged’ machines and worked on many more, but what I see now is the beginning of the end for the home country hobby machine producers who think that their products are better than everyone else’s.

 

When it came to rebuilding my shop, ready for retirement and taking on a few outside jobs, it was a choice of either buying one badged machine or a fully kitted shop with all the tooling and machines, it was a brain deader choice, and I have now jumped on the far eastern bandwagon, and haven’t regretted it one bit.

 

Bogs

[BogstandardParticipant @bogstandard]

 

Edited By Bogstandard on 21/06/2010 06:17:32

[john swift 1Participant @johnswift1]

Hi bogs ,
                   I totally agree with you
with hobby machines you have to spend time or money having parts fitted before you can use them.
closer to home , the prescot watch makers rested on  their lorals and look what happend to them.
an error repeated time and time again in this country.

I am starting off with a cl300 lathe  that needed  the speed control fixing
having reverse engineered the pcb ,thats now working. ( the day job helps with this bit )
Now the hard part , I have decided to change / upgrade the spindle bearings , before I start to use it
I think this  will help to make the parting off tools last longer for one thing.
 i don’t think an inverted parting off tool will help with this machine

having read a number of related threads on this forum i have a long list of mods to do

with hobby machines the term “precision” is miss used in the same way as “HiFi” to describe  cheap audio amplifiers.

most of the time you only get what you pay for

                                                                      john

Edited By john swift 1 on 21/06/2010 14:52:22

[DiggerParticipant @digger]

I too have far eastern machines and I’m not “knocking ” them they cost me little and can do a sterling job in the right hands, of course lots of machining work is now done on cnc machines with programmes written in the drawing office and sent down to the shop floor, but if you don’t have a skilled engineer and only semi skilled  operating the machines they cannot then be blamed for substandard work being produced, again it’s probably as you say bogs the assembly of the machine where problems should be picked up, I have seen some appalling examples of machined parts offered for sale as will most people at one time or another, but what I’m saying is, If the chap who is machining parts does not know and endmill from a windmill and has no idea how to even read a mic, or recognise a bad finish on a surface plate, then substandard work is to be expected.

[Sub MandrelParticipant @submandrel]

For what it’s worth not all Chinese stuff is crap. Mike Chrisp questioned the wisdom of me centering a gear for dicviding in the tail end of the bore of my chinese mini lathe’s mandrel. I checked the bore of my mandrel, and it was less than 1/2 a thou out – a hole that serves no official purpose other than somewhere to stick stock through. At the business end the spindle bore is as near true as I can measure.

 

Even a bar in the 3-jaw shows less than a thou runout three inches from the jaws, not bad for a cheap far-eastern chuck?

 

On the other hand I have had a few rogue bits – a no-name 3MT dead centre with the end visibly off centre – fortunately it was ‘soft’ enough to true up with a TCT cutter – it now runs 100% true.

 

Neil

[DiggerParticipant @digger]

Yes I was surprised at the accuracy of my three jaw chuck, I got it with the little colchester lathe from chester machine tools. If I’ve only paid a few quid for something I’m not too dissapointed if it’s not 100% perfect, I don’t mind doing a little work to bring it up to spec.

[Richard ParsonsParticipant @richardparsons61721]

 

Actually the only machine I have bought which ran true ‘straight from the box’ within its limits which were imposed by its design and materials was my Emcomat SL.  This was over 65 yesrs ago.   All the others (including my Myford Super7) have had to be ‘prepared for use’ after delivery. With the big Chinese lathe this took over 3 months of work. This work included evicting a piece of pink paper with Chinese characters on it which had jammed up and damaged part of cross slide feed. I do not read Chinese but I think it was part of a pestilence paper (or the curse of Ho Lin Wun the Chinese golfer).  In other words ir was stripped cleaned and re-buitl.

I now have to sort out a little problem on the cross slide which has developed too much ‘spring’. About 0.005”, from the look of it, this is annoying. I think it may be due to the plastic bed sweepers but I have not tracked it down yet, but I will.

Machines built in the Far East are produced by mass productions. If the QC people do not get after changes in production methods which are causing rejection you will get a bad product.

All machines need servicing to take up wear, looseness which develops with time etc. I do what I call a 6 months ‘clean’ and re-set everything with lots of ‘clocking’ and the use of the micrometers.  The next one is scheduled for the beginning of October when the weather cools but before it becomes too cold.

I admit none of my tooling is up to exhibition quality but it is accurate within the limits and my ability to measure this accuracy.

[DiggerParticipant @digger]

Hi Richard, Yes preventative maintenence is always a good idea, overall I am pleased with the accuracy of my little milling machine and mini lathe, and as has already been said i suppose that production methods and standards of work will improve over time, but unfortunately the cost of the products will also increase! of course the accuracy of a persons own work depends on their requirements, for the most part i have seen some truly fantastic work made for model engineering exhibitions, and if people can manufacture these type of engines and components in their home workshops using perhaps cheaper imported machine tools, they are indeed good engineers, which goes back to my earlier post, if we get a tool that is slightly under par (from Ho Lin Wun) we can always correct it and go on to manufacture first rate products

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